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A deburring strategy in drilled hole of CFRP composites using EDM process
Islam, Md. Mofizul,Li, Chang Ping,Won, Sung Jae,Ko, Tae Jo ELSEVIER SCIENCE 2017 JOURNAL OF ALLOYS AND COMPOUNDS Vol.703 No.-
<P><B>Abstract</B></P> <P>Carbon fiber reinforced plastic (CFRP) composites are highly promising materials for applications in the aeronautic and aerospace industry due to their superior strength-to weight and stiffness-to-weight ratios. Drilling of CFRPs composites is an important machining operation in the aerospace industry. However, during drilling of CFRPs, the formation of burrs are always severe shortcomings. In most machining processes, burrs are an undesired by-product cause many problems in assembly, inspection, process automation and precision component operation. To address this problem, this study introduced electrical discharge machining (EDM) as a deburring method for removal of burrs which are generated during drilling of CFRP composites. Four types of cylindrical tool namely copper, steel, brass and aluminium were used as the electrode for deburring. Deburring was carried out at various capacitance and time with different electrode materials. Experimental results demonstrated that the generated burrs of the drilled hole were successfully removed by the proposed deburring method. The copper electrode proved the better performance than others electrode in terms of deburring time and material removal rate. On the other hand aluminium electrode obtained lowest performance. The suggested deburring technique is effective for removal of the drilling burrs in conductive materials regardless of their hardness, because of the EDM deburring uses electrical discharge and its thermal energy without mechanical contact between the tool and workpiece.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A deburring method has been developed using EDM for removal of burrs from CFRP. </LI> <LI> Generated burrs of the drilled hole were successfully removed by the proposed method. </LI> <LI> Copper electrode obtained the highest performance among the four electrodes. </LI> <LI> No morphological changes were observed in drilled hole after deburring. </LI> </UL> </P>
Convex diamond patterns by grinding with a wheel which is dressed by a rounded tool
Md. Mofizul Islam,김호찬,Do Sup Han,Chang Ping Li,Tae Jo Ko 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.4
Patterned surfaces such as longitudinal micro-grooves, micro-dimples, and micro-convex shapes have great potential for improving tribological properties by reducing wear, friction, drag and lubrication consumption. Convex diamond patterns can be generated by a special grinding operation in which the wheel has a single helical groove on its circumference. To obtain such patterns, the same wheel needs two-way feed motion on the workpiece. The grooved wheel geometry determines the final patterns on the workpiece, so the development of a precise groove shape on the wheel surface is very important. The aim of this study was to generate convex diamond patterns by grinding with a specially grooved wheel and dressing. To make a precise groove on the wheel surface, a rounded-tip dressing tool was used in the dressing process. The resulting convex diamond patterns can be displayed by entering the input parameters into a simulation program developed using Matlab. The simulation result is compared with experimental results for verification. The simulation model could be used to control an actual grinding process or to predict the convex patterns on a flat surface.
Dry Electrical Discharge Machining for Deburring Drilled Holes in CFRP Composite
Md. Mofizul Islam,고태조,Chang Ping Li 한국정밀공학회 2017 International Journal of Precision Engineering and Vol.4 No.2
Dry electric discharge machining (EDM) is an evolving technology that uses gas as a dielectric instead of liquids like oil or deionized water. Dry EDM reduces machining costs and environmental hazards. Most studies on dry EDM deal with steel as the workpiece. Hence, this study investigates a dry EDM technique for the removal of burrs in drilled holes in CFRP composites. Oxygen and air was used as the dielectric medium, and the results were compared with a previous study on oil EDM. The material removal rate increased significantly with the capacitance, voltage, and gas pressure in both dry EDM and oil EDM. Positive tool polarity produced a higher material removal rate (MRR) than negative polarity in both cases. Compared to conventional oil EDM, using oxygen as a dielectric showed nearly three times better MRR, and that with air was two times better. Moreover, in dry EDM using oxygen as dielectric exhibited better performance than using air as dielectric. This study revealed that the dry EDM is more effective than that of oil EDM as a deburring technology.
Mechanism analysis of hybrid machining process comprising EDM and end milling
Li, Chang Ping,Kim, Min-Yeop,Islam, Md. Mofizul,Ko, Tae Jo Elsevier 2016 Journal of materials processing technology Vol.237 No.-
<P><B>Abstract</B></P> <P>STD 11 alloy steel is an extremely hard and difficult-to-cut material that is used extensively in cutter and die manufacturing for its superior wear resistance. This paper introduces a hybrid machining process (HMP) based on EDM and end milling (EDM-end milling) as an effective method for machining difficult materials. The HMP combines cutting action and an electrical thermal process. The machining mechanism was investigated, and a mathematical model of EDM-end milling is presented. Simulated and experimental cutting results were compared to validate the model. A tungsten carbide end mill was used as a tool electrode to machine STD 11 alloy steel (H<SUB>R</SUB>C 60) with different electric energy pulses. The results show that the method greatly improves tool wear and machining efficiency.</P>